1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus, an image processing apparatus, and an image processing method, which process an image obtained by X-ray radiography and X-ray fluoroscopy.
2. Description of the Related Art
There are generally two methods of generating an X-ray image by means of an X-ray diagnostic apparatus. One is a method using X-ray radiography and another is a method using X-ray fluoroscopy. Upon X-ray radiography, the X-ray diagnostic apparatus generates an X-ray having a dose enough to obtain a sufficient contrast in a single moment and generates an X-ray image. The X-ray image obtained by the X-ray radiography is referred to as a radiographic image. The radiographic image is an image having a high contrast, a high space resolution, and a high degree of accuracy. On the other hand, upon X-ray fluoroscopy, the X-ray diagnostic apparatus continuously generates less X-rays than the case of the X-ray radiography and continuously generates an X-ray image. The X-ray image obtained by the X-ray fluoroscopy is referred to as a fluoroscopic image. The fluoroscopic image is generated with X-rays less than that in the case of radiographic image is generated, so that it is possible to decrease amount of suffering from X-rays to a patient (object) and an operator. The fluoroscopic image is displayed as a moving image.
On the X-ray fluoroscopy, a treatment may be carried out by inserting a catheter, a guide wire or the like (hereinafter, for simplification, referred to as a wire) into an intended part of a body of a patient. In this case, it is very difficult to operate the wire only by the X-ray fluoroscopy because a contrast of the wire is very weak. Therefore, as an aid for operation of the wire, there is a roadmap method of generating a blood vessel image and displaying this blood vessel image and a wire image in piles (for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-87633).
Hereinafter, a flow of general processing of this roadmap method will be introduced. At first, an operator inserts a wire into a body of a patient upon X-ray fluoroscopy and promotes the wire to the intended part of the body. This fluoroscopic image having the wire drawn is referred to as a fluoroscopic live image. In addition, a fluoroscopic image having no wire drawn to be generated prior to the fluoroscopic live image is referred to as a fluoroscopic mask image. The X-ray diagnostic apparatus stores a fluoroscopic mask image upon X-ray fluoroscopy. The X-ray diagnostic apparatus generates a wire image as a subtraction image by subtracting the fluoroscopic mask image from the fluoroscopic live image to be continuously generated. The X-ray diagnostic apparatus displays the generated wire image and the blood vessel image generated in advance on X-ray imaging in pile in real time. On this displayed image, the wire moving on a blood vessel is displayed in real time. The operator promotes the wire to the intended part while observing this displayed image.
However, a body motion of the patient may be generated during X-ray fluoroscopy. If the body motion is generated, a displacement is generated between the fluoroscopic live image and the fluoroscopic mask image. As a result, an artifact such as a bone is generated on the wire image. In addition, in accordance with the displacement between the fluoroscopic live image and the fluoroscopic mask image, positions of a blood vessel drawn on the blood vessel image and a wire drawn on the wire image are displaced. As a result, it becomes difficult to observe the display image. In addition, it becomes difficult for the operator to promote the wire to the intended part.
In such a case, an artifact such as a bone is improved by removing the wire from the imaging area, X-ray fluoroscoping the patient once again, and regenerating a fluoroscopic mask image. However, according to this method, the displacement between the blood vessel image and the wire image is not improved. In order to improve this displacement, a new blood vessel image should be further generated. Therefore, an extra time (labor) and an extra radiation exposure are generated.